Articles made from lipophilic-rich cellulosic material and methods therefor

ABSTRACT

The invention relates to systems and techniques for manufacturing articles containing cellulosic material, a tackifier, and a binder, and related processes of making and using the cellulosic articles. In particularly exemplary embodiments, the manufactured articles are door skins, sometimes known as door facings, and doors made from the door skins. The article contains a lipophilic cellulosic material, a tackifier, and a binder.

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM TO PRIORITY

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/582,560, filed Nov. 7, 2017, which is incorporated herein byreference.

FIELD OF THE INVENTION

This invention relates to systems and techniques for manufacturingarticles from lipophilic-rich cellulosic materials, a tackifier, and abinder resin, and related processes of making and using the cellulosicarticles. In particularly exemplary embodiments, the manufacturedarticles are door skins, sometimes known as door facings, and doors madefrom the door skins.

BACKGROUND OF THE INVENTION

Man-made consolidated cellulosic articles, such as fiberboard,hardboard, medium density fiberboard and the like, can be press moldedor embossed to have three-dimensional shapes and/or various design andstructural features found in natural wood. The types of usefulconsolidated cellulosic articles are referred to by terms such as: (a)fiberboards such as hardboard (e.g., low-density or high-densityhardboard), soft board, medium-density fiberboard (MDF), high-densityfiberboard (HDF); and (b) chipboards such as particleboard andmedium-density particleboard. Such composite articles can be used asdoor skins (door facings), columns, floors, floor underlayment, roofsheathings, ceilings, walls, wall coverings, wainscots, partitionsystems, doors, and stairs in the construction of homes, offices, andother types of buildings, as well as furniture components, such aschairs, tables, countertops, cabinets, and cabinet doors, and otheruses, such as bulletin boards, for example.

Various processes can be used to produce consolidated cellulosicarticles, including wet-felted/wet press or “wet processes”;dry-felted/dry-pressed or “dry” processes; and wet-felted/dry-pressed or“wet-dry” processes. Such processes are discussed in further detail inU.S. Pat. No. 6,524,504, the disclosure of which is incorporated hereinby reference.

Conventionally, consolidated cellulosic articles typically include aformaldehyde based binder, such as phenol formaldehyde or ureaformaldehyde, to “glue” the fibers together. Formaldehyde binders arelow cost and compatible with the hydrophilic nature of cellulosic fiber,readily reacting with the high population of hydroxyl groups ofcellulose, hemi-cellulose, and lignin components of the fiber to bindthe fibers together.

Generally, wood fibers used to make cellulosic articles are hydrophilicin nature due to hydroxyl groups, which interact well with water.However, as sources for common wood fibers dwindle, alternative woodsources are considered. In certain countries, such as Malaysia, thegovernment has emphasized the use of alternate plantation, fast-growingtree species as wood fiber sources. Some alternate sources may be lessdesirable due to high lipophilic (hydrophobic) components, such aspitch, fatty acid, glycerides and di/triglycerides, steryl esters,alkanol esters, wax, sterols, terpene alcohols, etc., in their fibers(high lipophilic extractive). For example, Acacia is an alternate woodfiber source. Acacia wood fiber has been undesirable in makingconsolidated cellulosic articles due to its high content of lipophiliccomponents, which interfere with the efficacy of typical formaldehydebased binders. Applicant has discovered that lipophilic-rich woodfibers, such as Acacia fibers, are not compatible with commonly usedbinders in a typical blow-line resination process for thin MDF sheets,sometimes resulting in poor processing, such as fiber mat cracking, poorsurface quality, poor coatability, and/or poor glue adhesion. Blow-lineresination has a negative effect on the tackifying effect of theformaldehyde binders. Applicant has also realized that addingconventional UF resin through a blender (after a blow-line) can improvemat integrity, but results in poor board surface due to the formation ofresin spots, among other defects.

Therefore, there remains a need to develop formulations and processes toenable the use of lipophilic-rich cellulosic fibers in the formation ofconsolidated cellulosic articles without decreasing mechanical/physicalproperties.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, a composite article ismanufactured which contains a lipophilic-rich cellulosic material, atackifier, and a binder. The tackifier is diluted to a relatively lowconcentration to improve tackifier distribution on the lipophilic-richcellulosic material. In an embodiment, the tackifier is distributedthroughout the composite article. In another embodiment, the tackifieris located on the surface of the composite article.

A second aspect of the invention provides a method for making thecomposite article. In a first embodiment, the method comprises combiningthe cellulosic fiber material with a binder and a tackifier, forming acomposite mat, and pressing and heating the composite mat to form thecomposite article. The tackifier may be added through a blender to amixture of cellulosic fiber material and binder, preferably after theaddition of the blowline binder. In a second embodiment, the methodcomprises combining the cellulosic fiber material with a binder, forminga composite mat, depositing a tackifier onto the surface of thecomposite mat, and pressing and heating the composite mat to form thecomposite article.

Other aspects of the invention, including methods, processes, articles,compositions, formulations, intermediates, activated fibrous materials,systems, kits, and the like which constitute part of the invention, willbecome more apparent upon reading the following detailed description ofthe exemplary embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are incorporated in and constitute a part ofthe specification. The drawings, together with the general descriptiongiven above and the detailed description of the exemplary embodimentsand methods given below, serve to explain the principles of theinvention. In such drawings:

FIG. 1 is a drawing depicting a mat integrity test;

FIG. 2 contains drawings showing the top and bottom views of a pan forSamples A, B, C and D;

FIG. 3 contains drawings showing the top and bottom views of a pan forSamples E, F, G and H;

FIG. 4 contains drawings showing the top and bottom views of a pan forSamples I, J, D and G;

FIG. 5 contains drawings showing the mat surfaces for Samples i-iii;

FIG. 6 are drawings of electron micrographs of board surfaces;

FIG. 7 is a graph illustrating complex viscosity vs. time for differentresins at different dilutions;

FIG. 8 is a graph illustrating the tensile stresses of board samplesa-e; and

FIG. 9 is a schematic of a system for resinating the cellulosic fibers.

FIGS. 2-6 are drawings of photographs taken of the described subjectmatters.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Reference will now be made in detail to exemplary embodiments andmethods of the invention. It should be noted, however, that theinvention in its broader aspects is not necessarily limited to thespecific details, representative materials and methods, and illustrativeexamples shown and described in connection with the exemplaryembodiments and methods.

The cellulosic articles described herein may be formed fromlipophilic-rich cellulosic fiber material, which includes at least onelipophilic component. The lipophilic components can be present in thecellulosic material in an amount of at least 0.02 wt %, such as from0.02 wt % to 8 wt % or more, based on the total weight of the cellulosicfiber material. As used herein, “lipophilic-rich” means that thelipophilic component of the cellulosic material is at least about 2 wt%. Although lipophilic component amounts lower than about 2% may bepresent, at least about 2%, as determined by ethanol/toluene extraction(Pinto et al., Journal of Agricultural and Food Chemistry 2005, 53,7856-7862), is needed to be considered “lipophilic-rich” for the puposesof the present invention. Typically the acacia fibers contain lipophiliccomponents toward the high end of the range. For purposes of the presentinvention, the term “lipophilic component” is to be understood asmeaning that the lipophilic component is and, therefore, can beconsidered an impurity and/or a natural compound(s) found in thecellulosic material. Examples of lipophilic components include waxes,fatty acids, alkanols (e.g., white wax and/or long-chained OH compounds,such as C₂₄-C₂₈—OH, and/or high melting point alkanols of 90° C. orgreater), hydroxy extractives, fatty alcohols, triglycerides,dyglycerides, sterols, steryl esters, phospholipids, and the like.Examples of fatty acids include fatty acids with an alkyl group ofC₄-C₃₀, such as C₁₆-C₁₈ fatty acids, C₁₈-C₂₈fatty acids, and/or C₂₀-C₂₆fatty acids. The fatty acid can be saturated or unsaturated. A portionor all of the fatty acids can be bound or attached to other molecules,such as triglycerides or phospholipids. Other examples includetetradecanoic (myristic, C₁₄); hexadecanoic (palmitic, C₁₆);9,12-octadecadienoic (linoleic, C₁₈); 7-octadecadienoic (C₁₈);heptadecanoic (margaric, C₁₇) or octadecanoic (stearic, C₁₈); docosanoic(behinic, C₂₂); tetracosanoic (lignoceric, C₂₄); hexacosanoic (cerotic,C₂₆); and/or pentadecanoic (C₂₅). Another way to consider thisextractive content is as a) the total unsaponifiable content (e.g.,content of alkanols and sterols, and steryl esters); and b) the totalfatty acids content. The lipophilic cellulosic material may includeAcacia wood, Eucalytus wood, cypress wood, rice, wheat as annual fibers,or combinations thereof.

The lipophilic-rich cellulosic fiber material may be mixed withnon-lipophilic cellulosic fiber material (or common cellulosicmaterial). The common cellulosic material may include cellulosicmaterial derived from a lignocellulosic material or biomass.Lignocellulose is composed of carbohydrate polymers (cellulose,hemicellulose) and lignin, which is an aromatic polymer, that form thestructure of plant cell walls. Preferably, the selected lingocellulosematerial is hardwood and/or softwood. Suitable species of softwoodinclude, e.g., redwood, spruce, hemlock; and hardwood include, e.g,.oak, cherry, maple, poplar, hickory, birch, aspen. The wood may berefined or defibrated using a standard refiner/defibrator, or may beunrefined. The wood or other lignocellulosic materials discussed hereinalso may contain delignified fibers, if the fiber source is fromrecycled waste paper. Non-wood organic cellulosic materials that may beused in combination with wood or as an alternative to wood includestraw, kenaf, hemp, jute, bamboo culms, corn cobs, corn stover, otherfibrous plants, and any combinations of two or more of such materials.Prefereably, the more fibrous parts of such plants, such as the rinds,are used instead of the entire plants. Also, recycled materials that maybe used in combination with wood and/or other cellulosic materialsdescribed above or as an alternative thereto include recycled paper,pulp, or a combination including recycled paper and pulp.

The total cellulosic material (lipophilic and non-lipophilic) may be inthe form of particles, powder, fibers, chips, strands, flakes, shavings,sawdust, etc., or combinations thereof. The preferred cellulosicmaterial is fibers, particularly wood fibers suitable for use inmanufacturing fiberboard products. The average dimensions of length anddiameter for wood fibers are typically 3 mm and 20-35 micrometers forsoftwood species, and 1 mm and 20 micrometers for hardwood species. Forthermal mechanically refined wood fibers, such as used for MDFmanufacturing, certain portions of fiber furnish are fiber bundles(comprised of multiple individual fibers) that may have largerdimensions. Finer fibers have smaller dimensions especially with overrefining. Other sizes outside the above ranges may be used so long asthe cellulosic material is suitable for press molding. The cellulosicmaterial may be pre-processed and obtained as byproducts from wood millsor furniture plants and may be broken down to the desired size by usinghammermills or knives, as in flakers. The cellulosic material may be ina natural state and/or processed, for example, thermally refined and/ortreated for composite wood fiber panel products.

In particularly exemplary embodiments, the total cellulosic materialincludes relatively small particles, fibers, or other forms of wood. Theparticle or fiber size and distribution can be measured using a sievetesting device with a number of predetermined screens of different meshsizes. It should be understood that depending on final products andtheir applications, a wide range of size distributions are considered tobe well within the scope of the present invention.

Processing of the total cellulosic material may be performed using a dryprocess, a wet-dry process, or a wet process. In an exemplaryembodiment, a batch dry process is used. Generally, a dry processinvolves conveying the cellulsoic material entrained in a gaseous orvapor stream or by using a fluidized bed. Atmospheric air may be used asthe gaseous component of the fluidized bed.

The total cellulosic material may include about 20 wt % to about 100 wt% of the lipophilic-rich cellulosic material, preferably about 50 wt %to about 100 wt %, more preferably about 75 wt % to about 100 wt %. Thebalance of the total cellulosic material may include one or more commoncellulosic materials. In a preferred embodiment, the total cellulosicmaterial includes greater than about 25 wt % of Acacia fibers,preferably about 50 to about 100 wt %, with the balance being made up ofmixed tropial hardwood.

The lipophilic-rich cellulosic material is preferably mixed with abinder and dried before being treated with the tackifier. The tackifyingeffect of the binder and of the tackifier is reduced through blowlineaddition. The present invention also contemplates the addition of thetackifier after the combination of the lipophilic-rich cellulosicmaterial with the binder. For example, the lipophilic-rich cellulosicmaterial may be combined with the binder prior to being treated with thetackifier. The lipophilic-rich cellulosic material may be combined withthe binder and then treated with the tackier, as part of an in situprocess. The binder addition can be broken into two or more steps takingplace at different stages of the process, for example, to include insitu and ex situ treatment of the lipophilic-rich cellulosic materialrelative to the binder. For example, the binder can be added to thelipophilic cellulosic-rich material prior to the addition of thetackifier. Preferably, the lipophilic-rich cellulosic material is firstmixed with the uncured binder in a blowline 2 (see FIG. 9) where theagitated lipophilic-rich cellulosic material is sprayed with the binder.The agitation of the lipophilic-rich cellulosic material in the blowlinehelps disperse the binder more consistently throughout the mass of thelipophilic-rich cellulosic material. Agitation may be provided by asteam driven turbulance flow system under pressure as is typical in theMDF industry.

The binder may be an isocyanate, a formaldehyde resin, a protein-basedadhesive, or a combination thereof. The isocyanate component typicallyis a polymeric diphenylmethane diisocyanate (pMDI); however, otherisocyanates may also be employed. The formaldehyde resin typically is aurea formaldehyde (UF) resin, a melamine UF (mUF) resin, a phenolformaldehyde (PF) resin, or combinations thereof, such as PUT or PmUF.The preferred binder is UF, PF, or a combination thereof, at an add ratetypical in the MDF industry, 2-12 wt % based on total dry weight of thelipophilic-rich cellulosic material.

The binder and lipophilic-rich cellulosic material are then dischargedinto a dryer 4 (see FIG. 9), e.g. a flash tube dryer, to remove excessmoisture. Preferably, the dryer 4 uses hot air to heat and remove themoisture. Upon exiting the dryer, the moisture content (MC) of theresinated lipophilic-rich cellulosic material is preferably about 4 toabout 12%.

The dried lipophilic-rich cellulosic material is then further processedwith a tackifier. As used herein, “dried lipophilic-rich cellulosicmaterial” refers to the mixture of binder and lipophilic-rich cellulosicmaterial which has been dried. In a first embodiement, the driedlipophilic-rich cellulosic material is mixed with a tackifier to form acomposite mixture, comprising the cellulosic material, binder andtackifier. The tackifier is distributed throughout the mass of thecomposite mixture. The composite mixture may then be formed into acellulosic mat, which is subsequently consolidated under pressure andheat to form the article of the present invention. In a secondembodiemnt, the dried lipophilic-rich cellulosic material is formed intoa mat, whose top surface is then coated with the tackifier, e.g. such asby spraying, followed by surface drying. The coated mat is thenconsolidated under pressure and/or heat to form the article of thepresent invention. Thus, the first embodiment produces an article havingthe tackifier distributed throughout its mass; and the second embodimentproduces an article having the tackifier only on its surface.

In the first embodiment, the dried lipophilic-rich cellulosic materialis then treated with a tackifier. As used herein, the term “tackifier”is used to refer to a material which improves the cohesive strengthbetween the fibers and between the fibers and the fines, and promotesfiber entanglement. The tackifier has the attributes of making thefibers “sticky” and also causes them to become entangled together,particularly causing the chain ends to become entangled. The tackifiermay be diluted, e.g., with water. It is important that the dilutedtackifier, when added to the lipophilic-rich cellulosic material,sufficiently wets the lipophilic-rich cellulosic material whilemaintaining its tackiness. For example, when cellulosic fibers are used,the tackifier, when added to the fibers, should disperse onto the fibersand allow the fibers to adhere to each other. If the tackifier is notsufficiently diluted, its ability to disperse on the fibers isdiminished, which may lead to poor or incomplete adhesion of the fibers.Without being bound to any particular theory, it is believed that thetackifier is useful for imparting tack to the composite article while inproduction, e.g. while in a mat form. It is believed that due to thelipophilic nature of the cellulosic material, the binder alone impartsinsufficient tack to the wet composite article, e.g. mat, such that themat can be cracked prior to completion of pressing the compositearticle. Preferably, the diluted tackifier has a concentration of about5 to about 60 wt %, more preferably about 10 to about 40 wt %, and mostpreferably about 20 to about 40 wt %.

Tackifiers appropriate for the present invention may be, but are notlimited to, 1) acrylics, such as BASF Acrodur 950L (water based solutionof acrylic polymer), Dow Aquaset, such as Aquaset 400 and Aquaset 600(water based acrylic solution polymer); 2) isocyanates: availablecommercially as XR28404 from Stahl; 3) polyethylene imines (PEI); 4)polyvinyl amides (PVA); 5) polyamide amines (PAA); 6) polycarbodiimides(CDI): available commercially as XR5508 from Stahl; 7) phenolformaldehyde resin (PF): available commercially as GP1692 from GeorgiaPacific (GP); 8) urea formaldehyde (UF): avialable commercially asUF-ML01 from Hexion; 9) polyvinyl acetate (PVAc): available commerciallyas PVA-2360SP from IFS Chemicals; and 10) starch. The preferredtackifier is one or more acrylics, such as described in U.S. PublishedPatent Application Number 2013/0131223 A1 of Bouguettaya, incorporatedherein by reference, more preferably, high molecular weight and highviscosity acrylic tackifiers. As used herein, “high molecular weight”means that the polymer has a weight average molecular weight (Mw) offrom about 2,000 to about 3,000,000, preferably from about 20,000 toabout 1,500,000, and more preferably from about 200,000 to about650,000,. In certain embodiments, the polymer has a number averagemolecular weight (Mn) of from about 1,000 to about 2,000,000, preferablyfrom about 10,000 to about 1,000,000, and more preferably from about55,000 to about 100,000. In general, viscosity is proportional tomolecular weight, so higher molecular weight tackifiers tend to havehigher viscosity.

In certain embodiments, the acrylic contains i) a C₁ to C₂₀ alkyl(meth)acrylate, ii) an ethylenically unsaturated carboxylic acid, iii) avinyl aromatic group, iv) a vinyl ester of a C₂to C₁₃ alkyl carboxylicacid ester, v) a C₂ to C₈ hydroxyalkyl (meth)acrylate, vi) anethylenically unsaturated nitrile, vii) an α,β-ethylenically unsaturatedamide-group-containing compound, viii) a reactive vinyl cross-linker,ix) combinations thereof, or x) reaction products thereof. The C₁ to C₂₀alkyl (meth)acrylate can be methyl (meth)acrylate, ethyl (meth)acrylate,propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate,t-butyl (meth)acrylate, pentyl (eth)acrylate, hexyl (meth)acrylate,cyclohexyl (meth)acrylate, benzyl (meth)acrylate, 2-ethylhexyl(meth)acrylate, heptyl (meth)acrylate, n-octyl (meth)acrylate, nonyl(meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl(meth)acrylate, tridecyl (meth)acrylate, lauryl (meth)acrylate, stearyl(meth)acrylate, isobomyl (meth)acrylate, nobornyl (meth)acrylate,4-tertbutylcyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl(meth)acrylate, dimethyl maleate, n-butyl maleate, propylene glycol(meth)acrylate, carbodiimide (meth)acrylate, t-butylaminoethyl(meth)acrylate, 2-t-butylaminoethyl (meth)acrylate,N,N-dimethylaminoethyl (meth)acrylate, or combinations thereof.

In certain embodiments, UF and/or PF may be used as a tackifier as wellas a binder. When used as a tackifier, however, the UF or PF is morediluted (and thus, has a lower viscosity) than the same used as abinder. For example, when used as a binder, the solid content of UF isabout 60 wt % to about 65 wt %, but when used as a tackifier, the solidcontent is less than 50 wt %.

During the treatment process of the first embodiment, the tackifier ispreferably added to the dried lipophilic-rich cellulosic material in ablender 6 (see FIG. 9). The tackifier may be diluted before being addedto the blender or mixed with the diluent in-situ in the blender 6. Thedried lipophilic-rich cellulosic material may be introduced to theblender 6 at the same time as or before the tackifier. Preferably, thetackifier is added to the blender 6 in an amount of about 0.3 to about2% based on the weight of the lipophilic-rich cellulosic material (driedbasis), more preferably about 0.4 to about 1%. The tackifier is sprayedonto the fiber in the blender where the fiber and tackifier dropletsintermingle in turbulent spin-flow conditions. The blender may be ablender suitable for batch processing, although the present inventionalso contemplates a continuous process with tackifier being introducedinto a flowing turbulent stream of lipophilic-rich cellulosic material.

In the first embodiment, the composite mixture comprising the cellulosicmaterial, binder and tackifier may then be formed into a compositearticle by first forming the composite mixture into a cellulosic mat,and then consolidating the cellulosic mat under pressure and/or heat asin a typical MDF manufacturing process.

In the second embodiment, the cellulosic mat is formed from the driedlipophilic-rich cellulosic material and sent to the forming line 8 (seeFIG. 9) where the tackifier is coated, e.g. such as sprayed, on the topsurface of the cellulosic mat before consolidation under pressure and/orheat. The method of the second embodiment eliminates the need for theblender 6. In that case, it is possible to proceed directly to theforming line 8 from the drier 4.

The forming processes described, for example, in U.S. Pat. No. 5,543,234to Lynch et al. and U.S. Pat. No. 4,726,881 to Schultz may be used forthe present invention. The mat may include one or more layers of thecomposite mixture, and be made according to methods known to thoseskilled in the art. A “dry” production process, i.e. a typical MDFmanufacturing process, is preferred for the invention, but wet orwet/dry processes can also be considered. The composite article isformed by consolidating the mat in a press, typically under heat andpressure, according to methods known to those skilled in the art. Thecomposite mixture may be randomly formed into a mat by air blowing oneor more layers of the composite onto a support member. The mat,typically having a moisture content of less than or equal to aboutthirty weight percent (30% by total weight), and preferably 4-12 wt %,is then pressed under heat and pressure to cure the resin and tocompress the mat into an integral consolidated structure. For example,typical pressing conditions for thin MDF door skins (about ⅛″ inthickness) may include press temperature of about 270-350° F. with UFresin and fiber moisture content of about 10-12%, and 380-420° F. withPF resin and fiber moisture content of about 4-6%. Exemplary press cycletimes may be about 45-70 seconds.

During pressing, one or more reactions may take place between the binderand the cellulosic material, the tackifier and the cellulosic material,and/or the binder and the cellulosic material and/or combination of allthree. For example, condensation reactions between carboxlic acid (fromthe tackifier), hydroxyl (from the cellulosic material) and methylolgroups (from the binder) may take place during hot pressing. Dependingon the chemistry of the binder and the tackifier the tackifier may bereactive or inert with respect to the binder component and/or thecellulosic material. If bonding does occur between the tackifier andother components of the composite article, it may be physical and/orchemical bonding. Certain tackifiers may impart a degree of hydrogenbonding with the cellulosic material.

The pressed composite articles contain cellulosic fibers which containlipophilic components. However, upon treatment with the tackifier, thelipophilic-rich cellulosic fibers may be used to form composite articleswhich possess physical and mechanical properties similar to or betterthan those conventionally made from common cellulosic fibers, includingno fiber mat cracking prior to pressing, high surface quality, excellentcoatability, and/or excellent glue adhesion of the composite panels. Thecomposite articles produced may be (a) fiberboard, such as hardboard(e.g., low-density or high-density hardboard), soft board, andmedium-density fiberboard (“MDF”); and (b) chipboard, such asparticleboard, medium-density particleboard. Most preferably, thecomposite articles are door skins (thin MDF), such as typically used tomake solid core or hollow core doors.

Without further description, it is believed that one of ordinary skillin the art can, using the preceding description and the followingillustrative examples, make and utilize the articles of the presentinvention and practice the claimed methods. Resination and addition oftackifier were accomplished during initial testing by spraying onto airfluidized fiber using a lab scale blender consisting of a motor drivenfan in the bottom of a 22-liter stainless steel beaker. The treatedfiber with tackifier was formed into 8″×8″ fiber mats for the matintegrity test. It should be understood that the invention is not to belimited to the specific conditions or details described in the examples.

EXAMPLE 1 Mat Integrity Test for Articles Made by the First Embodiment

Acacia fibers (moisture content (MC) of 14-16%) were resinated with UFbinder and dried using an IR oven to a moisture content of 7-10% . Ifused, a tackifier was then added to the dried fibers. 100 g of fiberswere then used to make an 8″×8″ loose fiber mat and pressed to a stopwith a thickness of 12.7 mm at room conditions and then the pressure wasimmediately removed. Mats made with different tackifiers at differentsolids content and with different add rates were made and tested.

The compressed mat was subjected to a mat integrity test as illustratedin FIG. 1, where the compressed mat 2 was slid along and beyond a flatsurface 4. The distance d where the mat broke off is proportional to theintegrity of the mat, i.e., the larger the distance d, the higher themat integrity.

Mat spring back of the compressed mat (final mat height aftercompression) was also measured by a caliper.

Table 1 shows the results of the mat spring back and mat integrity testsof the following compressed mat samples:

Sample 1: Acacia fibers were resinated with 10% UF binder (with 59%solids), dried in a laboratory IR oven. UF (as tackifier) at a 2% addrate (based on dried fiber) was then added to the fibers. Resination andtackifier additions were made using a laboratory blender describedabove. A compressed mat was formed as described above. Target moisturecontent of the mat was 9-11 percent. Sample 1 was a control sample usedto observe the results where the invention was not implemented.

Sample 2: The same as Sample 1 except that the tackifier was Acrodur950L with 30% solids.

Sample 3: The same as Sample 1 except that the tackifier was DowChemical-Aquaset 400 with 30% solids.

Sample 4: The same as Sample 1 except that the tackifier was Stahl-CDI5508 with 30% solids.

Sample 5: The same as Sample 1 except that the tackifier was PEI with30% solids.

Sample 6: The same as Sample 1 except that the tackifier was IFS-PVAc2360SP with 30% solids.

Sample 7: Acacia fibers were resinated with 10% UF binder and 2% Acrodur950L with 30% solids (tackifier) and dried in an IR oven (no blendermixing was effected). Sample 7 was intended to simulate the addition ofthe binder and the tackifier at the same time in the blow line.

TABLE 1 Sample Mat spring back (mm) Mat integrity (in.) 1 32.5 4.50 231.1 5.25 3 31.0 5.50 4 31.3 4.50 5 28.7 4.25 6 32.5 4.00 7 32.0 3.75

The following observations are evident from Table 1:

1) Tackifiers Acrodur 950L and Aquaset 400 significantly improved matintegrity when compared to control Sample 1.

2) Tackifiers CDI and PEI made fibers very tacky (due to observed fiberagglomeration) but mat integrity values did not change much whencompared to control Sample 1.

3) It appears that a balance of fiber entanglement (resulting from evendispersion of tackifier on the fibers) and tackiness is needed toachieve desired mat integrity (see also Example 3 below).

4) Addition of the tackifier before IR drying did not improve matintegrity (see Sample 7).

EXAMPLE 2 Mat Integrity Test for Articles Made by the Second Embodiment

Acacia fibers (moisture content (MC) of 14-16%) were resinated with UFbinder and dried using an IR oven to a moisture content of 7-10% . 100 gof fibers were then used to make an 8″×8″ loose fiber mat and pressed toa stop with a thickness of 12.7 mm at room conditions and then thepressure was immediately removed. The tackifier was sprayed (with finedroplets) onto the top surface of the compressed mat and then matintegirty was evaluated before and after drying in the oven for 10 minat 140F.

-   Sample 8: The tackifier Acrodur 950L was sprayed on top of the    compressed mat.-   Sample 9: The same as Sample 8 except that the fiber mat was dried    in the oven.-   Sample 10: The tackifier UF (as tackifier) was sprayed on top of the    compressed mat.-   Sample 11: The same as Sample 10 except that the fiber mat dried in    the oven.

TABLE 2 Sample Mat spring back (mm) Mat integrity (in.) 8 30.7 3.5 930.7 >6.5 10 31 4 11 31 >6.5

From Table 2, surface coating of Acrodur 950L or UF as tackifier on thefiber mat and then drying of wet top layer resulted in significantlyimproved the mat integrity (see Samples 9 and 11 in Table 2).

EXAMPLE 3 Tack Turbulence Test

The tackifier was added to UF resinated fiber in the manner described inExample 1. 30 g of the dried fibers were added to a pan and shaken for10 min. using the agitation of a standard lab sift device. The amount offiber agglomeration in the pan was photographed in both top and bottomsides (FIG. 2-4) and visually evaluated.

Several samples were made and evaluated as follows:

Samples A, B, C and D) UF tackified fibers prepared, as described in thepreceeding paragraph, at 11.5% (Sample A), 14.7% (Sample B), and 17.6%(Sample C) moisture content (MC) by changing the solids content of thetackifier from 60% to 30% and 15%. Sample A was further dried, beforetackifier addition, to lower the moisutre content to 9.3% (shown assample D in FIG. 2).

Sample E) Acrylic (Acrodur 950L) tackified fibers prepared as describedabove at 14.2% moisture.

Sample F) Acrylic (Aquaset 400) tackified fibers prepared as describedabove at 13.3% moisture.

Sample G) Sample E was further dried, before tackifier addition, tolower the moisture content to 9.6% (shown as sample G in FIG. 3).

Sample H) Sample F was further dried, before tackifier addition, tolower the moisture content to 8.5% (shown Sample H in FIG. 3).

Sample I) CDI tackified fibers prepared as described above at 9.7%moisture.

Sample J) PEI tackified fibers prepared as described above at 8.5%moisture.

FIG. 2 shows drawings of the top and bottom views of the pan for SamplesA-D. Because the fibers agglomerate or clump, the sizes of theagglomerations are indicative of the clumping achieved with the varioussamples. The larger clumps in the drawings indicate higher fiberagglomeration/cold tack than the smaller clumps. It is apparent fromFIG. 2 that an increase in moisture content increases fiberagglomeration (compare Samples A, B, and C, and Sample D).

FIG. 3 shows drawings of the top and bottom views of the pan for SamplesE, F, G and H. The samples were made to compare different acrylictackifiers and MC. It is apparent from FIG. 3 that 1) lower MC reducesfiber agglomeration for both Acrodur 950L (compare Samples E and G) andAquaset 400 (compare Samples F and H); 2) lower amounts of loose fibersor higher agglomeration observed for the Acrodur 950L (Samples D and E)may be related to higher tackiness of this resin in comparison with UFresin; 3) lower amounts of fines is evident for the Acrodur 950L SampleD in comparison with Samples A and B; and 4) higher molecular weightand/or higher viscosity of Acrodur 950L (see FIG. 7 which showsviscositites for Acrodur 950L and Aquaset 400 (AQ400)) produces moreagglomeration in comparison with Aquaset 400.

FIG. 4 shows drawings of the top and bottom views of the pan for SamplesI-J, D, and G. It is apparent from FIG. 4 that CDI (Sample I) and PEI(Sample J) have high tackiness compared to Acrodur 950L (Sample G) evenat low MC.

EXAMPLE 4 Mat Surface Evaluation

Mats were made in accordance to the method described in Example 1. Thefollowing mat samples were made:

Sample i) 2% UF tackified fiber mat prepared at 8.5% moisture.

Sample ii) 2% Acrodur 950L tackified fiber mat prepared at 9.6%moisture.

Sample iii) 2% PEI tackified fiber mat prepared at 8.5% moisture.

FIG. 5 shows drawings of the mats made in Samples i-iii. It is apparentfrom FIG. 5 that 2% UF and Acrodur 950L tackifiers result in arelatively smooth mat surface (Samples i and ii, respectively), whilethe mat surface made with 2% PEI (Sample iii) appears relatively rough.Overall, Samples i, ii and iii show that the visual smoothness of themat surface may be correlated with high fiber to fiber entanglement (cf.FIG. 4). Even though PEI is tackier than Acrodur 950L, it results inpoor fiber entanglement and consequently lower mat integrity thanAcrodur 950L (cf. FIG. 4).

FIG. 6 shows drawings of scanning electron micrographs (SEM) of matsformed with barium sulfate labeled Acrodur 950L and UF tackifiers. Theblack dots (barium sulfate) on the SEM show areas rich in resins. It isapparent from FIG. 6 that resin distribution on the fibers is muchbetter with Acrodur 950L when compared to UF resin with high solidscontent (50%) as a control. Moreover, Acrodur 950L can be diluted to amuch lower solids content than UF. The increased dilution assists indistribution of the resin onto the fibers, which reduces resin spotissues on board surfaces. Dilution of the tackifiers reduces theirviscosity (FIG. 7) which significantly improves their distribution onthe fibers.

EXAMPLE 5 Mechanical Performance

Lab test boards were made using a lab press and pressing at 350° F. for1 minute at about 600-700 psi. Portions of the fiber mats made for themat integrity test (described in Example 1) were used to make thelaboratory test boards, which were subjected to tensile testing. A boardspecimen having dimensions of 5 cm (length)×1 cm (width)×about 0.3 cm(thickness) was pulled apart in a universal mechanical testing machine.The tensile stress at breakage of the specimen was recorded. Boardsamples were made as follows:

Sample a) Tackified fibers prepared as described in Example 1 using 2%UF tackifier at 50% solids.

Sample b) Tackified fibers prepared as described in Example 1 using 2%Aquaset 400 tackifier at 30% solids.

Sample c) Tackified fibers prepared as described in Example 1 using 2%Acrodur 950L tackifier at 30% solids.

Sample d) Tackified fibers prepared as described in Example 1 using 1.5%Acrodur 950L tackifier at 15% solids.

Sample e) Tackified fibers prepared as described in Example 1 using 1%Acrodur 950L tackifier at 15% solids.

FIG. 8 shows the tensile stresses of board samples a-e. It is apparentfrom FIG. 8 that resinating Acacia fibers with 2% Acrodur 950L/30%solids (Sample e) improves the mechanical properties of fiberboard whencompared with UF resin (Sample a) as a control. The addition of thetackifier Acrodur 950L (sample c) did not reduce the mechanicalintegrity as compared with the control board (sample a). In other words,there is a good bonding interaction among all three components, thelipophilic cellulosic fiber, the conventional binder, and the tackifier.

EXAMPLE 6 Full Size Door Skin Testing

The effect of two tackifiers, Aquaset 400 and Acrodur 950L, with variousadd rates was investigated to identify and eliminate mat cracking andresin spot defects. Mat cracking levels, noted as a percentage, andappearance of resin spots on the full size door skins are reported inTable 3. The Aquaset 400 tackifier was added to the mixed acacia fibersand binder. Addition of Aquaset 400 with 0.5%, 0.75%, 1% and 1.7% addrates eliminated successfully the mat cracking and resin spots on thedoor skins. Addition of Acrodur 950L with 1%, 1.25% and 1.7% add rateseliminated the mat cracking but did not reduce the resin spots on thedoor skins.

TABLE 3 Add Mat spring Mat Appearance of Tackifier Rate, (%) back, (mm)Cracking % resin spots UF- 625BL 1.70 33 0 Resin spots Aquaset400 1.7031 0 No resin spots Aquaset400 1.00 33 0 No resin spots Aquaset400 0.7532 0 No resin spots Aquaset400 0.50 30 0 No resin spots Acrodur 950L1.70 34 0 Resin spots Acrodur 950L 1.25 34 0 Resin spots Acrodur 950L1.00 31 0 Resin spots

Although certain presently preferred embodiments of the invention havebeen specifically described herein, it will be apparent to those skilledin the art to which the invention pertains that variations andmodifications of the various embodiments shown and described herein maybe made without departing from the spirit and scope of the invention.Accordingly, it is intended that the invention be limited only to theextent required by the appended claims and the applicable rules of law.

What is claimed is:
 1. A composite article comprising a lipophilic-richcellulosic material (LCM), a binder, and a tackifier.
 2. The compositearticle of claim 1, wherein the LCM is Acacia wood, Eucalytus wood,cypress wood, rice straws, wheat straws as annual fibers, orcombinations thereof.
 3. The composite article of claim 1, wherein thebinder is urea formaldehyde (UF), phenol formaldehyde (PF), melamineurea formaldehyde (mUF), polymethylene poly(phenyl isocyanates) (pMDI),or combinations thereof.
 4. The composite article of claim 1, whereinthe tackifier is an acrylic polymer, an isocyante, a polyethylene imine,a polyamide amine, a polycarbodiimide, a phenol formaldehyde resin, apolyvinyl acetate, a starch, or combinations thereof.
 5. The compositearticle of claim 4, wherein the tackifier is a high molecular weightacrylic polymer.
 6. The composite article of claim 5, wherein theacrylic polymer contains i) a C₁ to C₂₀ alkyl (meth)acrylate, ii) anethylenically unsaturated carboxylic acid, iii) a vinyl aromatic group,iv) a vinyl ester of a C₂ to C₁₃ alkyl carboxylic acid ester, v) a C₂ toC₈ hydroxyalkyl (meth)acrylate, vi) an ethylenically unsaturatednitrile, vii) an α,β-ethylenically unsaturated amide-group-containingcompound, viii) a reactive vinyl cross-linker, ix) combinations thereof,or x) reaction products thereof.
 7. The composite article of claim 6,wherein the C₁ to C₂₀ alkyl (meth)acrylate is methyl (meth)acrylate,ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate,isobutyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate,hexyl (meth)acrylate, cyclohexy (meth)acrylate, benzyl (meth)acrylate,2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, n-octyl(meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl(meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, lauryl(meth)acrylate, stearyl (meth)acrylate, isobomyl (meth)acrylate,norbornyl (meth)acrylate, 4-tertbutylcyclohexyl (meth)acrylate,3,3,5-trimethylcyclohexyl (meth)acrylate, dimethyl maleate, n-butylmaleate, propylene glycol (meth)acrylate, carbodiimide (meth)acrylate,t-butylaminoethyl (meth)acrylate, 2-t-butylaminoethyl (meth)acrylate,N,N-dimethylaminoethyl (meth)acrylate, or combinations thereof.
 8. Thecomposite article of claim 1, wherein the tackifier is coated onto thesurface of the article.
 9. The composite article of claim 1, wherein thetackifier is distributed throughout the mass of the article.
 10. Thecomposite article of claim 1, further comprising non-lipophiliccellulosic material, wherein the non-lipophilic cellulosic material andthe lipophilic cellulosic material form a total cellulosic material. 11.The composite article of claim 10, wherein the total cellulosic materialcomprises about 20 wt % to about 100 wt % of the LCM base on the totalweight of the total cellulosic material.
 12. The composite article ofclaim 10, wherein the total cellulosic material comprises more than 25wt % of Acacia fibers, with the balance being made up of mixed tropicalhardwood
 13. The composite article of claim 1, wherein the ratio of thetackifier to the LCM is about 0.3 to about 2 wt %, and the ratio of thebinder to the LCM is about 2 to about 12 wt %.
 14. The composite articleof claim 1, wherein the composite article comprises about 10 to about 98wt % of the LCM.
 15. The composite article of claim 1, wherein the ratioof tackifier to the LCM is about 0.3 to about 2 wt %.
 16. The compositearticle of claim 1, wherein the ratio of binder to LCM is about 2 toabout 12 wt %.
 17. The composite article of claim 1, wherein the articleis a door skin.
 18. A method for making a composite article, comprisingthe steps of: a) mixing a lipophilic-rich cellulosic material (LCM) witha binder to provide a binder rich LCM; b) drying the binder rich LCM toprovide a dried LCM; c) mixing the dried LCM with a tackifier to providea composite mixture; d) forming a cellulosic mat from the compositemixture; and e) consolidating the cellulosic mat to form the compositearticle.
 19. A method for making a composite article, comprising thesteps of: a. mixing a lipophilic-rich cellulosic material (LCM) with abinder to provide a binder rich LCM; b. drying the binder rich LCM toprovide a dried LCM; c. forming a cellulosic mat from the dried LCM; d.coating at least one surface of the cellulosic mat with a tackifier; ande. consolidating the coated cellulosic mat to form the composite article20. The method of claim 19, wherein the coating step involves sprayingthe cellulosic mat with the tackifier.